Former "Fringe" star Lance Reddick is slated to star in the Season 7 finale of "Castle."

TV Line reports that who Reddick will play and the overall theme of the episode is being tightly kept under wraps, with series runner David Amann simply telling reporters the show will "focus on compelling, high-stakes story-telling surrounding Castle and Beckett mythology," and that it would surely offer a "satisfying end to the season‎."

As for Reddick, his status with the show was only revealed when co-star Penny Johnson (Captain Victoria Gates) recently tweeted a photo of him on the set.

Entitled "Hollander's Woods," the episode is also expected to star former CSI vet Wallace Langham and to delve into Castle's (Nathan Fillion) Season 6 disappearance on his wedding day. Some of this season's initial episodes touched upon that mystery, but recent shows have seemingly put that plotline on the back burner.

In an interview with TV Guide, executive produce David Amann explained that fans deserve to know why Castle disappeared. 

"We always knew that the missing time was not going to stay a mystery for the entire season," Amann said. "We felt like we owed the audience more than just a tease on what happened in that missing time, and we feel like we deliver a fairly coherent and complete accounting of what happened. There are some outstanding questions that remain at the end of all this, but the primary question of where he was and what he was involved with are largely answered by the end of the episode." 

Meanwhile, ABC network executives have yet to publicly state if "Castle" will be returning for an eighth season and recent reports hinted even if it does, the status of Det. Kate Beckett (Stana Katic) very much remains up in the air. Both Katic and Fillion's contracts are slated to expire at the end of the season, but Fillion recently inked a new deal pending the show's ongoing status.

Earlier this year, Katic told TV Line, "If the character is complete, if there is nowhere else to go creatively, then I think it's better to stop when you're on top. [F]or me it's about art over finance, and as long as we're creating something that is compelling and that has nowhere to go, then we're good to go. And when we find that we're not... then it's time for everyone to pack up and move onto the next thing."

Creator Andrew Marlowe told TV Guide that writing a finale without knowing if it's the real ending of the show was complicated. But this means that the finale of Season 7 will give fans closure in case it does not return.

"Castle" airs on Mondays at 10 p.m. EST on ABC.